Electrical connector clamp



April 1966 D. c. HUBBARD ETAL 3,248,684

ELECTRICAL CONNECTOR CLAMP Original Filed Nov. 13, 1962 2 Sheets-Sheet 1INVENTORS. Dav/d C. Hubbard BY Vernon Hellsfer'n April 6, 1966 D. c.HUBBARD ETAL 3,248,684

ELECTRICAL CONNECTOR CLAMP Original Filed NOV. 15, 1962 2 Sheets-Sheet 21 1 :9 INVENTORS. Dav/d C. Hubbard Vernon fiells'ferfi WMMTM UnitedStates Patent 3,248,684 ELECTRICAL CONNECTOR CLAMP David C. Hubbard,Centralia, and Vernon Hellstern,

Webster Groves, Mo., assignors to A. B. Chance Company, Centralia, Mo.,a corporation of Missouri Original application Nov. 13, 1962, Ser. No.237,204. Divided and this application May 4, 1964, Ser. No.

1 Claim. (Cl. 339-95 ducting surface coatings, such as oxides, areadequately pierced or sufiiciently removed from the conductors beforeattempt is made to establish the electrical connection therewith.Scraping, brushing and other techniques can, of course, be usedsuccessfully but they are time consuming and care must be taken toassure proper and adequate removal or break through.

Where dependence is made on the grounding of an electrical circuit forprotection of workmen, or for the joining of two electrical conductorsfor the transmission of electric power, it is absolutely necessary thatthere be a good, low resistance electrical path established at the pointof connection. Every effort should be made to remove or penetratenonconducting oxides between the conductors and the connector to avoidthe insulating or undesirable high resistance effects of these surfacecoatings.

carelessness or forgetfulness on the part-of workmen in removing theoxides present a condition of potential hazard; hence, it is the mostimportant object of the instant invention to provide a connector thatwill assist in establishing a low resistance electrical contact with theconductor as the connector is manipulated during its installation suchthat its serrations may scrape away oxides without need for auxiliarytools or brushes for this purpose.

Another object of this invention is to provide a clamp or connectorhaving teeth capable of piercing the thin but resistance-inducing oxidesof lightly oxidized conductors workmen may misconstrue as like new andhence not requiring scrubbing action, such teeth being nondamaging tothe conductor.

Still another object is to provide for means to assure full and firmcontact by all the conductor-engaging teeth when the connector isclamped tightly to the conductor following scrubbing actions.

A further object-of the instant invention is the provision of aconnector that causes the teeth to scrub away the oxides as the resultof a rotative action on the conductor and as a function of drawing theconnector tight.

Another important feature of the instant invention is the provision ofreplaceable inserts for jaws of clamps wherein the inserts are providedwith teeth of the aforeextended parallel groove clamp made pursuant toone form of the present invention;

FIG. 2 is an elevational view showing the opposite sidethereof;

FIG. 3 is an inside view of one of the elements of the clamp;

FIG. 4 is a transverse cross-sectional view showing the clamp prior todrawing it tightly against the conductors;

FIG. 5 is a view similar to FIG. 4 showing the clamp tightly against theconductors;

FIG. 6 is a fragmentary, side elevational view of a multiple anglegrounding clamp having replaceable inserts made according to a modifiedform of the present invention;

FIG. 7 is an end view of the clamp shown in FIG. 6;

FIG. 8 is a fragmentary cross sectional view taken on line 8-8- of FIG.6; and

FIG. 9 is a fragmentary cross sectional view taken on line 99 of FIG. 6.

The present invention provides a clamp for interconnecting a pair ofelectrical conductors and includes a pair of elements interconencted bya stud bolt. Each element is extruded or otherwise formed from aresilient, metallic or other conductive material and provided with twopairs of spaced, serrated, conductor-engaging faces disposed on oppositesides of the bolt. The inner, curved faces of the elements are such thatwhen the bolt draws on the elements, their faces move into positionsconcentric to and in full engagement with the conductors, which isaccomplished by the elements deflecting under the force required to drawthe members tightly against the conductors. The serrated faces presentconductor-engaging teeth which bite through and, by rotative action,scrub away the oxides and thereby electrically connect with theconductors.

One of the elements is provided with the projections engageable with thebolt for movement toward the latter so as to providebolt locking meansas the elements deflect under the force required to draw the membersagainst the conductors.

The clamp shown in FIGS. 1-5 of the drawings is broadly denoted by thenumeral 10 and includes a pair of clamping elements 12 and 14, andfastening means in the nature of a bolt 16 interconnecting the elements12 and 14. The clamp 10 is adapted to be utilized for interconnecting apair of electrical conductors 18 and 19 therebetween, although, as willhereinafter become apparent, the principles of the instant invention arealso applicable in situations where connection is to be made with but asingle conductor.

The element 12 is provided with an opening 20 for loosely receiving thebolt 16, head 22 of the latter being engageable with outer, convexsurface 23 of the element 12. The element 12 is further provided with apair of spaced, elongated, transversely arcuate, fine serrated, innerfaces disposed on opposite sides of the opening 20 and presenting sharp,conductor-engaging teeth 25.

The element 14 is -provided with a pair of similar conductor-receivingsurfaces disposed on opposite sides of the bolt 16 when the latter isthreaded into the tapped bore 28 extending through the element 14 andnormally aligned with the opening 20 of the element 12. These surfacesare serrated for presenting a number of sharp teeth 32 similar to theteeth 25, such teeth 25 and 32 being formed and disposed for bitingthrough oxides of the conductors 18 and 19 to effect positive electricalinterconnections.

The element 14 is further provided with a pair of pro jections 34 on itsouter surface 30 embracing the bolt 28. Projections 34 are disposed forengaging bolt 16 and to this end they are partially threaded inalignment with the bore 28.

The elements 12 and 14 are preferably formed by an extrusion processfrom a material capable of deflecting,

. 3 such as an aluminum alloy, since such a material has efficientelectrical current-carrying capabilities, is relatively inexpensive,rugged in construction, resistant to corrosion, and of a naturerendering it capable of being easily extruded.

In use, the conductors 18 and 19 are placed between elements 12 and 14as shown in FIG. 4, and the bolt 16 is manipulated to draw on theelements 12 and 14, thereby moving the teeth 25 and 32 into engagementwith the convex outermost surfaces of the conductors 18 and 19. Theelements 12 deflect under the pressure and take the shapes illustratedin FIG. 5 when elements 12 and 14 are drawn tightly in place.

The projections 34 move toward each other and at the same time grip thethreaded portion of the bolt 16 therebetween to provide locking meanstherefor. Thus, a considerably greater torque is required to loosen thebolt 16 than would be required in the absence of projections 34.

Since the conductors 18 and 19 are generally exposed to the atmosphereduring normal use, a film or coating of non-conductive oxidation formson their surfaces. Teeth 25 and 32 bite through but scrub away suchfilms or coatings to provide an electrical path of minimum resistancecapable of efficiently transmitting electrical currents and effectivelyresisting the damaging and injurious efiects of short circuits and surgecurrents.

In order to understand the principles involved for accomplishing suchresults, it must first be recognized that if the recesses or arcuategrooves containing the teeth 25 and 32 were initially concentric withthe conductors 18 and 19 (i.e., when in the condition of FIG. 4) theforces of the bolt 16 would produce an eccentric relationship. This hasbeen one of the faults of conventional connectors. When fully clamped,the only zones which actually engage the conductors tightly are thosenext adjacent the bolt 16. Such results are caused by the inward flexingof the material at the bolt andbetween the conductors. This in turncauses the outer wings of both elements to flex or spring apartresulting in a tight grip only along a small portion of the concavefaces 'of the connector.

In the instant invention, on the other hand, as seen in FIG. 4, theelements 12 and 14 are initially arched outwardly. Also, the concavefaces are not initially concentric with the conductors 18 and 19.Instead, when the bolt 16 first brings the elements into engagement withthe conductors 18 and 19, only. the outermost of the teeth 25 and 32,i.e., those remote from the bolt 16 are in contact with the conductors18 and 19.

Then, as the bolt 16 is gradually tightened, the median zones of theelements 12 and 14 adjacent and around the bolt 16 begin to bendinwardly, pulling the four wings or jaws of the elements 12 and 14inwardly around the conductors 18 and 19 in a rotative manner. This notonly gradually forms the jaws into conformity with the shapes of theconductors 18 and 19, but pulls the teeth 25 and 32 inwardly across theconductors 18 and 19.

The inwardly rotative shifting of the teeth 25 and 32 across theconductors 18 and 19 produces a scraping or scrubing action which wipesaway the oxide crust and causes the teeth 25 and 32 to come into contactwith the conductive material of the conductors 18 and 19 beneath theencrustations.

The results are somewhat dependent also on the nature of the teeth 25and 32 themselves. The V-shape configuration, as shown, has been foundsatisfactory, but most important is that the serrations be very fine andthat the long 'edges of the teeth 25 and 32 be rather sharp. Also, theymust extend lengthwise of the conductors 18 and 19 rather thantransversely thereof.

When such care is taken in producing the teeth 25 and 32., the properscrubbing action, above explained, is accomplished and the sharp edgesactually cut through the n-oncondutive coatings without damage to theconductors themselves.

The additional function of the teeth 25 and 32 in cutting through theoxides must take place in a manner to avoid weakening of the conductorsas would be true if the teeth gouged into the conductive body of theconductors beyond the surface coatings. It has been found that the useof a large number of closely-spaced, fine serrations that are rathershallow will accomplish the described results when they are formedlongitudinally of the conductors as shown. Then, when the coatings havebeen scrubbed away and cut through by the teeth, there is a full andsafe engagement by all of the teeth with the conductive material of theconductors 18 and 19 as depicted in FIG. 5. And it must be rememberedthat such firm and positive electrical connection is also caused in partby the form of the jaws and the inward bending 'of the elements 12 and14, as above explained.

In the embodiment of our invention illustrated by FIGS. 6 to 9inclusive, there is depicted a clamp broadly designated by the numeral100 that includes a pair of clamping elements or jaws 112 and 114provided with inserts 112a and 114a, respectively. I

The jaws 112 and 114 are carried by a support 116, shown only fragmentarily in FIG. 6 for swinging movement toward and away from eachother by virtue of pivot bolts 117 and 121. The jaws 112 and 114 aremoved toward each other by a spreader device (not shown) that movesbetween their inner ends 112b and 114b, respectively. They are yieldablyheld apart by a compression spring (not shown) interposed therebetweenimmediately above the pivots 117 and 121 within the support or basestructure 116.

Inasmuch as the jaw 112 includes a pair of fingers or sections 112adisposed to receive the jaw 114 there/between when the jaws are movedtoward each other, there are in fact two inserts 1120, one for eachfinger 112C, respectively, as seen in FIGS. 7 and 9, whereas the jaw 114has but one insert 114a as seen in FIG. 8. Suitable fasteners 123 areprovided for holding the inserts on their corresponding jaws renderingthe same replaceable.

The inserts 112a are each provided with an elongated, transverselyV-shaped, finely serrated inner face, presenting sharp,conductor-engaging teeth 125. The insert 114a is provided with a similarconductor-receiving surface, serrated for presenting a number of sharpteeth 132 similar to the teeth 125, such teeth 125 and 132 being formedand disposed for biting through oxides of a conductor that is grippedbetween the inserts 112a and 114a so as to effect positive electricalinterconnection.

In all essential respects the serrations or teeth 125 and 132 performthe same function of establishing the electrical interconnection and insubstantially the same manner as above described with respect to theteeth of the clamp shown in FIGS. 1 to 5 inclusive. Although the jaws112 and 114 and their inserts 112a and 114a will perhaps not have thedegree of resilience as the jaws of the modification first hereinabovedescribed, nonetheless, much the same scrubbing action on the oxidetakes place when the jaws 112 and 114 are swung relatively toward eachother to move the inserts 112a and 114a into engagement with theconductor. Additionally, in the case of the clamp shown in FIGS. 6 to 9inclusive, it is possible to swing or rotate the clamp about the cableor conductor, thereby utilizing the teeth and 132 as a scrubbing mediumso as to remove the oxides and assure proper electrical contact betweenthe teeth 125-132 and the conductor.

It can now be seen that there has been provided a reliable, lowresistance electrical contact with reference both to system reliabilityin the transmission and distribution power and to the added security ofcarefully applied gr-ounding equipment. The heavy currents that mayproduce a hazardous condition where any connector is inadequatelyapplied in a grounding situation is also damaging to electrical circuitsinadequately joined. The contacts hereinabove described materiallyreduce the pos sibility of human error.

Having thus described the invention, what is claimed as said axes andextending in generally tangential relanew and desired to be secured byletters Patent is: tionship to said conductor when the latter is clampedA clamp comprising: between the jaws, first and second opposed,generally C-shaped jaws said structure mounting said sections indisposition to adapted to receive an electrical conductor there- 5receive said second jaw therebetween as said jaws are between, said jawshaving replaceable inserts each moved toward each other, whereby toadapt the having an inner V-s-haped surface provided with a clamp for awide range of conductor diameters. series of relatively fine serrationspresenting a large number of teeth having parallel, elongated cuttingReferences Cited by the Examiner edges 10 UNITED STATES PATENTSstructure mountlng said aws for swinging movement toward and away fromeach other about respective 1,786,369 12/1930 Terrell et 339 95 spaced,substantially parallel axes with said edges 1,844,011 2/1932 H extendingin substantial parallelism to said axes and 1,981,796 11/1934 Blsseu 339266 X spaced .circumferentially of said conductor when the 15 2,078,8464/1937 Gouldlng et X latter is received by the jaws; and 2,221,92311/1940 Passauermeans connected with said jaws for shifting the same2,270,807 1/1942 Johnson 339 246 toward and away from each other,whereby to grip 215521924 5/1951 Athy et said conductor when the latteris received by the jaws 2,679,032 5/1954 Thomas et a1 and, by virtue ofsaid swinging movement, assist 3,002,173 9/1961 Allen 39114X inscrubbing away nonconductive coatings on said FOREIGN PATENTS conductorto establish a low resistance contact as said edges bite through thecoatings, 1,154,750 11/1957 Francesaid first jaw including a pair ofelongated, substantially parallel clamping sections spacedlongitudinally of JOSEPH SEERS, Examlmlfi

